The present invention relates to an enhancing or facing process for a manufactured article through powder coating and to an apparatus for carrying out the same. The term "manufactured article" is to be understood for all purposes of the present specification as comprising any metal article, e.g. section bars, metal sheets, to which coating powder can be applied according to any suitable industrial method.
Facing processes by means of powder coating are currently employed for decorating metal section bars as an imitation of a wood grain, to be used particularly for obtaining window or door casings and frames.
After being suitably prepared for powder coating, metal section bars undergo a working cycle comprising the following operative steps: initially a first powder coating layer or primer is laid out on the section bar; then partial polymerisation of the first coating layer takes place; successively a second powder coating layer different in colour or tonality from the underlying layer is applied according to a predetermined graphical configuration and finally baking is effected to completely polymerise both the first and the second coating layers.
The above-described coating process, although affected by some drawbacks that drastically limit its industrial applications, in so far as both mass production and total costs of the final manufactured article are concerned. The most critical step for such a working cycle turns out to be the application of the second coating layer, i.e. of the decorative layer, which task often committed to the experience and ability of qualified personnel capable of reproducing specific graphical configurations, e.g. a fake wood grain, on any metallic and non-metallic support, by working manually and making use of conventional tools, e.g. brushes and paintbrushes.
From the above, it be easily understood that it impossible to carry out an industrial process comprising a completely manual operation, in that the latter results in an unavoidable economically unbearable bottle-neck that heavily slows down the entire production cycle.
Attempts made to transform the facing process for manufactured articles from a substantially manual process to an automatized one, althogh, on the one hand, they made it possible to speed up the production cycle, on the other, they showed to fall short of giving satisfactory results as to quality in terms of wood resemblance, as they would require permanent manual intervention by specialized personnel downstream of the working cycle.
The main object of the present invention is to provide a facing or enhancing process for manufactured articles through powder coating to eliminate or substantially reduce the above mentioned drawbacks affecting conventional coating techniques.
An important object of the present invention is to make it possible that by means of the above-said process fake wood grain coating with a very high degree of wood resemblance is obtained in such short times as to be suitable for use in a completely automated working cycle and to do without any manual operation by specialized personnel.
Another object of the present invention is that by means of the above-said process it is possible to obtain a fake wood grain coating on manufactured articles at highly competitive costs owing both to an increase in productivity for the whole coating plant and a reduction of costs of specialized labour.
A still further object of the present invention is that the above-said process is applicable to both vertical and horizontal coating plants.
Not a last object of the present invention is to provide a vertical fake wood coating apparatus which makes it possible to obtain production levels equivalent to those of standard monocolor coating plants, while ensuring high quality aestethic results at the same time, in terms of resemblance to a desired wood grain.
According to a first aspect of the present invention there is provided a process for facing or enhancing at least one manufactured article by means of powder coating according to claim 1.
Conveniently, the said process comprises controlling the said roller to perform linear displacements in the longitudinal direction of the or each manufactured article and to rotate around its own axis with a speed of rotation corresponding to a rolling peripheral velocity of said roller lower than its linear displacement velocity, in order to cause the said roller to roll and slide on the or each manufactured article.
According to another aspect of the present invention there is provided an apparatus according to claim 4 for carrying out the said process.
Advantageously, said support and handling means comprise at least one lever pivoted to a respective cursor element and suitable for performing controlled angular movements with respect thereto and at least one linear actuator having one end thereof articulated to its respective cursor element and its other end linked to its respective lever and being suitable for controlling said controlled angular movements of said lever to shift its respective roller between said working position and said rest position.
Further aspects and advantages of the present invention will better appear in the following detailed description of some currently preferred embodiments, given by way of non limiting examples with reference to the accompanying drawings, in which :
In the accompanying drawings similar or same parts or components have been identified with the same reference numerals.
With reference first to Figure 1, a plant 1 which is dedicated to imitation wood powder coating according to the invention, as shown by a block diagram and identified with reference number 1, can operate according to a working cycle comprising two or three stages depending upon whether two or three coating layers, respectively, are provided for the manufactured article to be decorated.
Plant 1, designed to carry out a two-stage working cycle, preferably comprises a first coating station 3 for applying a first powder coating layer, a fixing station 4 arranged downstream of the first coating station 3 and suitable for causing partial polymerisation of the first coating layer, a second powder coating station 5 for laying a second powder coating layer and a working station 6 for the final baking of both the first and the second coating layers.
Between the second coating station 5 and the final baking station 6, an apparatus 7 is provided, in which the process for enhancing manufactured articles 2 can takes place. Such a process comprises causing the manufactured article to undergo a rolling treatment, thereby obtaining, on the second coating layer not yet fixed and uniformly distributed on the manufactured article 2, a drawing or pattern as an imitation of wood grain.
As shown in Figures 2, 3 and 4, apparatus 7 preferably comprises a frame 8 comprising a base 9, a pair of side uprights 10 and 12 rising from base 9 and defining an intermediate vertically extending working area 13, and an upper crosspiece14 supported by the side uprights 10 and 12 and arranged to delimit zone 13 at the upper end thereof.
More particularly, as can be seen in Figure the working area 13 of apparatus 7 is crossed by an overhead conveyor 15 designed to support the manufactured article 2 in a vertical position and to convey it through the various working stations of plant 1. Advantageously, conveyor 15 is equidistant from the two side uprights 10 and 12 so that manufacture 2 is caused to follow, in use, a trajectory coinciding with the x-x center line of working area 13.
Moreover, side uprights 10 and 12 are provided with vertical guides 16 and 17 facing the working area 13, along which guides a respective mobile unit 18a and 18b is arranged to slide between a top and a bottom dead center, so as to be displaced, in use, close to the top end and the bottom end, respectively, of the manufactured article 2 in vertical trim.
As is better shown in Figure 3, mobile unit 18a and likewise mobile unit 18b preferably comprises a carriage 19 having a body 21 endowed with rollers or wheels 23 for rolling engagement with its respective vertical guide 17 and top 24 and bottom 25 end portions which are integral with body 21 and project therefrom towards working area 13.
To the bottom portion 25 of carriage 19 a fork 27 is secured, e. g. by means of bolts 26, which comprises a pair of side shoulders 28 arranged to support, at the free ends thereof, an oscillating pivot 29 acting as a linking element for a pair of levers 30 with respect to the carriage 19.
Each lever 30, having one longitudinal end 31 pivoted to the oscillating pivot 29 and its other longitudinal end 32 articulated to a shaft 33 whose rotation axis y-y supports a roller 34, is controlled, in use, so as to perform controlled angular movements around oscillating pivot 29, by a linear actuator 35, whereby shifting roller 34 between a working position, at which its lateral surface 36 is in contact with manufactured article 2 to be enhance or faced (see Figure 3), and a rest position , at which roller 34 is withdrawn from manufactured article 2 (as shown in Figure 2).
Linear actuator 35 can comprise, e.g. by a piston-and-cylinder unit mounted on the carriage 19, the cylinder 37 being pivoted to the bottom end portion 25, whereas the free end 38 of its piston 39 is articulated to its respective lever 30 at a linking pivot 40 located at a predetermined distance from oscillating pivot 29 of lever 30, thereby converting, in use, the back and fro movements of piston 39 with respect to cylinder 37 into closer to, and away from, movements, respectively, of roller 34 with respect to the manufactured article 2.
Advantageously, roller 34 is bound to rotate integral with shaft 33 that is caused to rotate, in use, by a motor 44 and controlled by an encoder (not shown in the drawings), both being arranged coaxially with axis y-y.
Moreover, to the longitudinal ends of shaft 33, on the side opposite to roller 34, two arms 42 are fixed and designed to support a horizontal pivot 45, which in turn bears a plurality of sucking means 49 suitable for removing the coating powder gathered on lateral surface 36 of roller 34 during the rolling treatment carried out on manufactured article 2.
As shown in Figure 3, and in particular in Figure 4, sucking means 49 comprise a series of suction orifices 50 in communication with a suction tube 51 and suitable for removing the coating powder retained during the rolling treatment, by lateral surface 36 of roller 34 and to convey it through sucking tube 51 towards a suitable storage and disposal reservoir (not shown in the Figures).
The use of suction means 49 is fundamental to ensure proper cleaning of lateral surface 36 of roller 34, since the same is advantageously in bas-relief according to a desired original that is to be reproduce on the surface 11 to be enhanced or faced of manufactured article 2.
As shown in Figures 5 to 8, on the lateral surface 36 of roller 34 a coating layer 52 of resiliently deformable material can be applied, having a working face 53 having a sequence of peaks 54 and recesses 56, suitably formed in it depending upon the graphical result meant to be obtained on the manufactured article 2.
As a matter of fact, when one wishes to reproduce a grain 55 which is an imitation of a specific type of wood on the surface 11 to be enhanced of manufactured article 2, on the working face 53 of coating layer 52 peaks 54 and recesses 56 are formed which extend randomly substantially in longitudinal direction of the coating layer 52 (see Figures 5 and 6). Once coating layer 52 has been laid, as described above, on roller 34, while the latter was rolling on the manufactured article 2 at a peripheral speed equal to the displacement speed of the moving carriage 19, working face 53 adheres only at its peaks 54 to the surface 11 to be decorated, on which a uniform powder coating layer has been previously laid. In this way, coating powder is locally removed, i.e. only at the peaks 54, thereby precisely reproducing onto it the drawing formed on working face 53.
Figures 7 and 8, instead, show a coating layer 52 with its working face 53 having a sequence of peaks 54 and recesses 56 shaped as concentric semicircles, by means of which it is possible to obtain, by causing roller 34 to roll and slide on the manufactured article 2, such a coating powder distribution on the surface to be decorated 11, as to reproduce a plurality of knots 57 as an imitation of a wood grain (as shown in Figure 9).
Advantageously, both mobile units 18a and 18b can comprise one or more brushes 22 fixedly mounted on their respective oscillating pivot 29 and integral in rotationg therewith, and a motor 66 suitable for moving brushes 22 to a desired position in order to cause them to work, in use, with a correct inclination of their bristles sliding against the surface 11 to be enhance of manufactured article 2.
The operation of the apparatus 7 is illustrated in Figures 10 and 11 showing the carriage 19 while being displaced forward, and meanwhile rolling and brushing operations of the surface 11 to be enhanced are carried out, and while being displaced backwards, respectively, with roller 34 and brushes 22 of the carriage 19 being at rest.
The forward stroke starts, preferably, when carriage 19 is at its top dead center. The roller 34 is then brought in contact with the surface 11 to be decorated by means of an angular movement of levers 30 controlled by piston-cylinder unit 35 about the oscillating pivot 29.
Should one wish to effect rolling by making roller 34 to roll onto the manufactured article 2, in combination with a downwards linear shift obtained by causing carriage 19 slide along its respective vertical guide 17, motor 44 is controlled to cause, in use, roller 34 to rotate about its own axis y-y, so as to obtain a rolling peripheral speed at the contact line between roller 34 and manufactured article 2 equal to the vertical displacement speed of carriage 19.
Rolling with no sliding of the roller 34 on manufactured article 2 makes it possible for the working face 53 of coating layer 52 to adhere without sliding to the face 11 to be decorated and fot the coating powder previously uniformly deposited on the surface 11 to be decorated to be retained at the peaks 54, thereby leaving a mark exactly reproducing the original drawing provided on working face 53.
In order to obtain, instead, rolling with sliding of the roller 34 on the manufactured article 2, it is sufficient that motor 44 causes roller 34 to rotate about axis y-y, so that its peripheral rolling velocity is slower than the vertical displacement velocity of carriage 19. In this case, the mark obtained on the face 11to be decorated does not exactly reproduce the original provided on the working face 53 of coating layer 52, but a distorted image thereof suitable for reproducing knots 57 of a desired wood grain.
As shown in Figure 9, apparatus 7 is suitable for providing an imitation wood coating on a manufactured article 2, having both veins 55 and knots 57, typical of a milled wooden surface.
Such a result can be obtained by combining the rolling treatment by means of roller 34 with a brushing treatment by means of fixed brushes 22 provided with bristles sliding, in use, on the surface 11 to be decorated.
A two working stage plant 1 can effect brushing treatment and rolling tretment simultaneously by arranging, during the forward displacement of carriage 19, the brushes 22 in contact with the surface 11 to be decorated, while roller 34 is already in its working position. When carriage 19 reaches the bottom dead center, brushes 22 are caused to stop by a control unit (not shown in the Figures) at an angular position detected by an encoder (not shown in the drawings), at which position the bristles ob brushes 22 are no longer in contact with manufactured article 2, and are held in that position during the entire return displacement of carriage 19.
To obtain grains 55 on the surface 11 to be decorated, apparatus 7 can include comb members (not shown in the Figures), instead of brushes 22, which comb members are mounted on a respective carriage 19 to effect with it an alternate straight movement. Each comb member comprises a plurality of tines of flexible material, which are spaced at a uniform or irregular pitch, have their free ends sharpened or flattened and are suitable for sliding, in use, on a manufactured article 2.
The powder coating proces, the plant and the apparatus for carrying out the same as described above are susceptible to numerous modifications and variations within the scope of the claims.
Thus, for example, as shown in Figure 1, plant 1 can operate according to a three coating stage working cycle that can be carried out by providing, between the above described apparatus 7 and the final baking station 6, a fixing station 60 suitable for causing partial polymerisation of the second coating layer just treated, a third coating centre 61 arranged to apply a third powder coating layer having colour, tonality and/or organolectic properties different from those of the underlying second layer, and a second apparatus 7 designed obtain a wood imiotation in the third just laid coating.
With such a plant 1 it is then possible to obtain wood grains 55 and knots 57 in two separate phases and on two different coating layers, with the advantage of distinguishing one from the other by providing powder coatings of different colour or tonality.
Preferably, wooden grains 55 are obtained in the first apparatus 7 through a brushing or a rolling treatment with no bristles sliding on the second coating layer just laid on the manufactured article 2.
In order to carry out the brushing treatment, apparatus 7 is set as shown in Figure 12, in which roller 34 is moved away from the surface 11 to be decorated and brushes 22 are brought into their working position and caused to shift in a vertical direction by the carriage 19 along a respective guide 17, thereby sliding on the surface 11 to be decorated in order to remove part of the second coating layer to obtain a plurality of grains 55 on it.
In the second case, indeed, grains 55 are obtained by roller 34 rolling on the manufactured article 2, on which roller a coating layer 52, as shown in Figure 5, is laid.
Once fixing of the second coating layer thus treated has been effected and the third powder coating layer has been laid, the rolling and sliding treatment takes place at the second apparatus 7 and a coating layer 52, as shown in Figure 7, is lapplied to roller 34 for that purpose.
In practice, materials as well as dimensions can be various according to requirements.